Traditional seats were designed so that the seating portion of the seat was at a right angle to the backrest. These seats, however, proved to be uncomfortable to sit in during long trips or flights. In an effort to improve the comfort level of seats, manufactures have tried various designs including increased padding in the seat and backrests as well as installing lumbar cushions in the lower portion of the back rest in an attempt to relieve pressure in the lower back of the seat occupant.
Another way of making seating more comfortable was to incline the seat with respect to the backrest. The inclination of the seat by approximately 2-6° allows the weight of the occupant to be transferred toward the intersection of the seat bottom with the back rest. This reduces the fatigue on the gluteus maximus that results from sitting directly on one's bottom for extended periods of time.
Although the angling of the seat bottom with respect to the back rest provides for greater comfort over an extended period of time, such an arrangement is not always possible or practicable. For example, in an aircraft passenger seat, the seat bottom or pad is angled at between 2-6° for taxi, take-off, and landing (TTOL). The seat bottom could remain at this angle throughout the flight, however, should one attempt to work at a desk or tray table, or eat sitting at this angle they would have to move up to the edge of the seat or lean forward so as to be able to write or avoid dropping food down the front of themselves. This type of seating is not necessarily desirable, particularly for executive-style seating on private or VIP aircraft.
It would be much more practical to work or eat in a chair in which the seat bottom was flat as opposed to being oriented at approximately a 6° angle. For this reason, a seat having a drop down seat pan that could be positioned either flat or angled approximately 6° from the horizontal would be an important improvement in the art.